I have no idea how to make tie downs with water pipe and steel plate, but having worked in the trucking industry, I have seen some creative solutions. If you can get to a car wrecker, you should be able to get some long seat belts fairly cheap. Then figure out how long you need your tie downs, and cut the seat belt to length. You'll want to melt the cut ends so the fabric doesn't fray and then put in some grommets on either end. To attach your new tie downs, you'll need to add a short length of heavy duty bungee cord (to each end) or even use a rubber inner tube from a bicycle (with some MacGyving). The seat belts are incredibly strong, and should work for almost any application. If you don't think that will work for you, then perhaps you could reply with a bit more information on the type of load you need secured and weight etc.

Do you want to make a post that you can bury in the ground to chain a dog too?

Take your steal pipe and weld it to the plate the bury it. If you don't have a welder then use threaded steal pipe with a flange. Be sure to use heavy duty lock tight or JB weld on the threads so it can't be unscrewed. Then bolt the flange to the plate and bury the whole thing.